When I first got my Kindle, I spent some time looking for a very (very!) simple way to batch convert my existing jpg files to greyscale (colour renders poorly on the Kindle) images of the appropriate size for my Kindle 3.

There are many options, but none of which were suitably easy to use. However, I did find that any joe can create an Applescript to do this. It's ridiculously easy.

As it may save other readers the notional effort of creating their own script, I attach mine. It outputs to a file called "Kindled" on the desktop. You may need to create such. Simply drag and drop any file or folder with source jpgs on it.